This program has two goals: development of new methods of immunosuppression and elucidation of the mechanism whereby malignant lymphomas develop in immunosuppressed individuals. New methods of immunosuppression will be sought in the natural immunoregulatory systems of the body. Specifically, we will determine if suppressor T cells or their secretory products can inhibit immune complex-mediated glomerulonephritis. We will also seek methods of increasing the immunosuppressive potency and specifity of T cells by treatment of donors with either antibody or antigen. The relationship between immunoregulation and malignant lymphomas will be studied with particular reference to defective feedback control of the immune response. We want to know the roles of both antibody and T cells in this system. Also the hypothesis will be tested that C-type oncornaviruses -- which are not necessarily oncogenic -- are immunoregulatory.